Arc lamp or the like



Sept. 2, 1952 R. c. BEITZ 2,609,519

ARC LAMP OR THE LIKE Filed July 21, 1950 I NVENTOR E/HHED C. BE/TZPatented Sept. 2, 1952 ARC LAMP OR THE LIKE Richard C. Beitz, Amherst,N. Y., assignor to American Optical Company,

Southbridge,

Mass., a voluntary association of Massachusetts Application July 21,1950, Serial No. 175,058

This invention relates to are lamps, welding apparatus and the likewherein one or more movable electrodes or the like are employed, andmore particularly to electrical and mechanical means for automaticallymoving such electrode or electrodes for automatically effecting an arcand for adjusting the arc to a proper predetermined size when theapparatus is placed in operation, as well as for automatically advancingsaid electrode or electrodes thereafter toward the are when required formaintaining said are at a substantially constant size as the electrodeor electrodes are consumed during use.

While the invention is especially useful in arc lamps which are to beused with photomicrographic apparatus wherein a substantially constanthigh intensity light source is needed and wherein freedom from vibrationduring photographing and such, particularly atvextremely highmagnifications, is essential, it nevertheless has general utility forcontrolling the size of arc in projectors, welding apparatus, electricarc furnaces and the like. Accordingly, hereinafter when the wordselectrode or electrodes are used, it should be kept in mind that theyare intended to apply to the electrically conductive arc sustainingmembers or materials ordinarily encountered in such apparatus. Theapparatus of the present invention is of such construction andarrangement that it may be, by the mere pressing of a switch,alternatively used on A. C. or D. C. current. Also the operatingmechanism of the present invention is of such high sensitivity that whenthe same is being used in an arc lamp, no appreciable visible change inintensity of the arc will be noticeable during ordinary use thereof.

' It is, accordingly, an object of the present invention to provide inan arc lamp or like apparatus efiicient, highly sensitive andinexpensive means for gripping and guiding an electrode or a pair ofelectrodes and for automatically moving the same so as to establish anare, so as to immediately thereafter automatically adjust the arc toproper predetermined size and so as to maintain the are substantiallyconstant during continued use thereof.

It is an additional object of the invention to provide in an arc lamp orlike apparatus automatically operable means of the type described whichmay be readily operated on alternating or direct current, as desired,while still retaining the high degree of sensitivity desired.

" It is, also, an object of the invention to provide in apparatus of thecharacter described, readily adjustable means for altering the prede- 6Claims. (01. 314-71) termined size of are which is to be automaticallymaintained during operation of the apparatus.

Other objects and advantages of the invention will become apparent fromthe detailed description which follows when taken in conjunction withthe accompanying drawing in which:

The single diagrammatic figure thereof indicates parts of an arc lamp orthe like and the electrical and mechanical means for operating same.

Referring to the drawing in detail, there is shown at l2 and M,respectively, a pair of electrodes or carbons which may serve toestablish and maintain an arc of suitable size at a point is in an arclamp or the like. Mechanism for advancing these electrodes toward eachother is diagrammatically shown herein and comprises suitable means forattaching the electrodes to a pair of endless chains or belts l5 and H,which are caused to move in opposite directions for advancing theelectrodes. The belts I5 and I1 are actuated by means of a pair ofshafts l8 and l 9 geared together by means of gears 20 and 22. In thedrawing, electrode I4 is shown as somewhat thicker in diameter thanelectrode l2 and gear 22 is of greater size than gear 20 for the purposeof obtaining the proper rate of advance of the electrodes as they areconsumed, While the apparatus will be first described for use with D. C.current, it should be noted that in cases where" an A. C. current is tobe employed for operation of the arc, electrodes of different sizesmight be employed instead of the ones shown. Gear 22 is actuated byshaft l9 which is in turn driven by reduction gear means 24 driven by amotor 26. In a preferred construction, means 24 and motor 26 may besuitably incorporatedin a unitary electric motor housing with gear means24 having a speed reduction ratio in the neighborhood of to 1.Whileendless belts have been shown in the drawing to move theelectrodes, it will be obvious that grooved pressure rollers could bearranged, as is well known in the art, to move the electrodes l2andl4.

The electrode [2 is connected by suitable means to a main electricalconductor 28 while electrode I4 is connected to a terminal of athree-wayseparable connector 30 and then at 32 is connected to one endof a heavy-duty ballast resistor 3.4. The opposite end 35 of the ballastresistor is in turn connected to another terminal of separable connector30 and then to a second main electrical conductor 36, so that externalelectric current may be supplied to the apparatus by means of conductors28 and 36. The reason for using a armature 38 and a pair of field coilst9 and 4-2,

with one terminal of the armature and of each field coil connectedtogether ata common. point. Such a motor is often referred'to as a,split-field series type motor since the twofield coils thereof act inopposition to each other in accordance with the current flowingtherethrough. and,

through the armature and the direction of operation of the motoraccordingly depends upon which field coil magnetic fiux dominates. Inthe present invention, the opposite freeterminal of the field coil 40 isconnected to a resistor 44, of suitable electrical characteristics,which in turn is connected to main conductor 28. The opposite freeterminal of the other field coil '42 is in turn connected to a, suitablefixed resistor 46 of suitable electrical characteristics which in turnis connected to an adjustable resistor 48 and this resistor. in turn isconnected to main conductor 36. The opposite free terminal of thearmature 38 is connected through the separable connector 30 preferablyto an intermediate point 50 on ballast resistor 34 adjacent the end 32of the resistor to which electrode it is connected or even at this endas determined by the operative characteristics of the control circuitand the mechanical characteristics of the arc lamp as will be presentlydescribed.

It will benoted that the electrical system just described is in effect aWheatstone bridge circuit in which two arms of the bridge extending frompoint 56 common with conductor 28 through the electrodes [2 and M and,ballast resistor 34 to point 58 common with conductor 36 constitute aprimary circuit 54,,with the point 50 common to these two arms. Theother two arms of this Wheatstone bridge are formed by field coil 45 andresistor 44 and by the field coil 42 and resistors 46 and 48,respectively, and together constitute. a secondary circuit 69. Thecommon point previously referred to and to which one armature terminalis connected is. indicated at 62, while the opposite armatureterminalthereof is connected to point 50, and preferably intermediate thearmature and point 62 a normallyclosed precision snap-action switch 63or thelike is connected.

The Wheatstone bridge control circuit just described operates in thefollowing manner. Assuming that the lamp is to be operated on D. C.

current and that the electrodes are in spaced.

relation at the time it is to be placed in operation by connecting theconductors to this "source of power, the electric current being suppliedwill fiowfrom point 58 mainly through ballast resistor 34 to point 50and then through armature 38 and switch 63 to point 62. Only anegligible amount of current will pass through resistors 46 and 48 andfield coil 42 to point.62 due to the high impedance and resistancethereof as compared with that through the armature and ballast. Currentfrom point 62 will pass through field coil 40 and resistor 44 to point56. When such flow of current occurs motor 26 will be energized tooperate the drive mechanism for the electrodes in a forwardly directionthereby advancing the electrodes toward point i6 and this advance willbe rapid since the current fiow through the armature at this time willbe comparatively large. This forward travel will continue until contactbetween the electrodes is established.

Immediately thereafter the resistance through the electrode containingarm of the bridge will drop, thereby allowing nearly all or the greaterpart of the main line voltage to be developed ,across the part of theballast between points and 58. Accordingly, only negligible current willflow-at suchxtime through the arm of the bridge containing field coilbecause of the high impedence' and resistance therein. Thus coil 52 andarmature 38 will be subjected to the main line voltage, therebyenergizing motor 26 to operate in the opposite direction. This willcause the electrodes I2 and l l to move. apart.

until the resistance in the electrode containing arm of the bridgeincluding the resistance across, the are at It builds up to such a pointthat the bridge circuit is substantially in balance, with the potentialsat points 58 and 62 substantially.

equal. Of course, mechanical friction and such will always be presentand will tend. to prevent the motor from retracting the electrodes allthe way to provide a perfectly balanced bridge. Consequently, thearmature will remain. stationary while the electrodes burn back to. andsufiiciently beyond this balanced condition so as to increase thevoltage drop in this arm of the bridge relative to that in the armbetween points Y and 58 and thus produce an out-of-balance condition ofsufficient magnitude to cause field coil til to be energized morestrongly than field coil 42. This condition will cause armature 38 torotate in a forward direction at a very low rate of speed, particularlywhen a reduction gear unit with aratio of approximately to 1 is providedin the driving system for shaft l9, and in a more or less continuousmanner.

The forward rotation of the armature. to ad vance the electrodes orcarbons will not always be of a uniformrate; since certain conditions,such ashard andsoft spots in the carbons, may cause the carbons at timesto burn away at varying rates. However, when these variations occur, thespeed of the motor will change in such a way as to maintain the currentthrough the ballast and the electrodes at a substantially constantvalue, which is synonymous with keeping the ratio of the voltage dropsacross the ballast: resistor and across thecarbons at a substantiallyconstant value. 7 v

It will be noted that the armature is connected at the intermediatepoint 59 in the ballast resistor instead of being connected at the end32.

The purpose for thisis to provide at all times,

a certain small amount of resistance in the arm of the bridge containingthe electrodes and, between points Ell-and 56, thereby giving greaterdriving torque in the forward direction of rotation of the motor than inthe reverse direction. Also frictionalresistance in the operating partsof the driving mechanism and such. willafterthe. arm is; struclr andbefore the motor becomes operative to move the electrodes forwardl'y,and thereafter the motor will always tend to drive in a forwardlydirection; thus preventing hunting which might otherwise result when amore evenly balanced bridge condition exists.

The ratio of the resistance in the secondary circuit 60 as compared tothe primary circuit 54 may be varied slightly by adjustment of therelatively light weight resistor 48 and this control may be used to varywithin desired limits the normal spacing which is to be maintained atgap it during normal operation of the apparatus. In fact resistance 48could be placed in either arm of the secondary circuit 60 and could bereadily arranged to provide the control desired.

When the lamp is to be used with alternating current, electrodes ofequal diameter may be substituted in place of electrodes 12. and [4. Theonly other change needed for operation on A. C. current then would beeither the omission of resistors 44 and 46 from the secondary circuit 60of the bridge or if desired, and as shown in the drawing, the resistance14 and 46 could be in effect eliminated by the closing of switches 64and 66 for short circuiting the resistors. In fact, such might beaccomplished, as is obvious, by the mere use of a single double-poleswitch controlling both resistances at the same time.

The-normally closed switch 63 in the armature circuit is so positionedthat it may be actuated by a cam 68, when the electrode l2 has beensubstantially consumed, for interrupting the current fiow through thearmature 38 and thereby preventing further forward movement of thedriving mechanism. For convenience during operation of the lamp, thereis provided a normally open switch 16 arranged in series with a pilotlight 12 and connected to points 50 and 56, which will be energized whenswitch is closed and this switch is preferably so positioned relative tocam 68 and switch 63 that shortly prior to the end of the operatingstroke of the mechanism a warning signal will be given by the pilotlight so the operator may replace the carbons before attempting to usethe lamp for any appreciable period of time thereafter. Such has beenfound to be useful particularly in photomicrographic work requiringexposures of appreciable duration, thus avoiding undesired interruptionof the arc during such photographing of specimens and the like. Whileopposed movable electrodes are shown and described above, it will beunderstood that, when desired, only one electrode need be movable forutilizing the automatic control means disclosed.

Having described my invention, I claim:

1. In an apparatus of the character described, the combination of a pairof electrodes for establishing and sustaining an arc therebetween, aballast resistor having one end thereof connected to one of saidelectrodes, a pair of main conductors, respectively, so as to provide asectrodes and to the opposite end of said ballast resistor,respectively, so as to place same in series relation in a primarycircuit, gripping and guiding means constructed and arranged so as tomove at least one of said electrodes toward and away from the other whenactuated, driving means including a rotatable electric motor foractuating said gripping and guiding means, said motor having a pair offield coils and an armature with a lead from each connected together ata common point, said field coils being arranged in said motor in opposedrelation to each other s0-- as to tend to rotate said'motor in oppositedirections when energized, means for connecting the opposite leadsofsaid field coils to said main conductors connected to the other of saidelecondary circuit therebetween, and means for connecting the other leadof said armature to said primary circuit at a point adjacent theconnection of said one electrode to said ballast resistor,

2. In an apparatus of the character described, the combination of a pairof electrodes for establishing and sustaining an arc therebetween, aballast resistor having one end thereof connected to one of saidelectrodes, a pair of main conductors connected'to the other of saidelectrodes and to the opposite end of said ballast resistor,respectively, so as to place same in series relation in a primarycircuit, gripping and guiding means constructed and arranged so as tomove at least one of said electrodes toward and away from the other whenactuated, driving means including a rotatable electric motor foractuating said gripping and guiding means, said motor having a pair offield coils and an armature with a lead from each connected together ata common point, said field coils being arranged in said motor in 0D-posed relation to each other so as to tend to rotate said motor inopposite directions when energized, means for connecting the oppositeleads of said field coils to said main conductors, respectively, so asto provide a secondary circuit therebetween, and means for connectingthe other lead of said armature to said ballast resistor at a pointintermediate the ends thereof.

3. In an apparatus of the character described, the combination of a pairof electrodes for establishing and sustaining an arc therebetween, aballast resistor having one end thereof connectedto one of saidelectrodes, a pair of main conductors connected to the other of saidelectrodes and to the opposite end of said ballast resistor,respectively, so as to place same in series relation in'a primarycircuit, gripping and guiding means constructed and arranged so as tomove at least one of said electrodes toward and away from the other whenactuated, driving means including a rotatable electric motor foractuating said gripping and guiding means, said motor having a pair offield coils' and an armature with a lead from each connected together ata common point, said field coils being arranged in said motor in opposedrelation to each other so as to tend to rotate said motor in oppositedirections when energized, means for connecting the opposite leads ofsaid fieldcoils to said main conductors, respectively, so as to providea secondary circuit therebetween, said last mentioned means including areadily adjustable resistor in series relation in said secondary circuitfor controlling the normal spacing of said electrodes during theoperation thereof, and means for connecting the other lead of saidarmature to said primary circuit at a point adjacent the connection ofsaid one electrode to said ballast resistor.

4. In an apparatus of the character described, the combination of a pairof electrodes for establishing and sustaining an arc therebetween, aballast resistor having one end thereof connected to one of saidelectrodes, a pair of main conductors connected to the other of saidelec trodes and to the opposite end of said ballast resistor,respectively, so as to place same in series relation in a primarycircuit, gripping and guiding means constructed and arranged so as tomove at least one of said electrodes toward and away from the other whenactuated, driving means including a rotatable electric motor foractuating said gripping and guiding means, said motor having a pairotfield coils and an armature with a lead from each connected togetherat a common point-said. field coils being arranged in saidv motorinopposedrelation to each other so as to tend to rotate said-motor inopposite directions when energized,,,means' for connecting the oppositeleads of said field coils to said main conductors, respectively,,so.asto provide a secondary circuit therebetween, said'last mentionedmeans including a. readily adjustable esistor in seriesrelation in saidsecondary circuit for controlling the normal spacing of said electrodesduring the operation thereof, and meansfor connecting the other-lead ofsaid armature to said ballast resistor at a point intermedi ate the endsthereof.

5. In apparatus of the character described and adapted to operateselectively upon alternating or direct current, the combination of. apairof electrodes for establishing and sustaining an arc therebetween, aballast resistor having one end thereof connected to one of saidelectrodes, a pair of main conductors, connected to the other ofsaidelectrodes and to the oppositeendof said ballast-resistor,respectively, so as to place same in series relation in a primarycircuit, gripping and guiding means constructed and'ar-ranged'so as tomove at least one of said electrodes toward and away from the otherwhenactuated, driving means including; arotatable electric motor foractuating said grippingandguiding means, said motor having a pair offield coilsv andan armature with a lead from each connected together at,a common point, said field coils :being. arranged in said motor inOpposed relation to each other so asto tend: torotate said motor inopposite directions whenenergized, means for connectingthejoppositeleads ofsaid fieldic-oils to said main conductors,respectively, for .operationon direct current, said lastmentioned meansincluding .a resistor of predetermined value .in series relation witheach field coil therebyproviding a secondary circuit between.said'conductors which includes said common point, readily operableswitch: means connected across each resistor and operable to eliminatethereffect of said resistors inssaid secondary circuit when it isdesired to operate said apparatus on alternating current, and: meansconnecting-the other lead of said armature to said, primary circuit at apoint adjacent the conneotionroi said one electrode to said ballastresistor.

6. In apparatus of the character described and adapted to operateselectively upon alternating or direct current, the combination of apair of electrodes for establishing and sustaining an arc therebetween,a ballast resistor having one end thereof connected to one of saidelectrodes, a pair of main conductorsconnected to the other of saidelectrodes and to the opposite end of said ballastresistor,respectivelmso as to place same in series relation in a primary circuit,gripping and'guiding means constructed and arranged so as to move: atleast-one of said. electrodes toward and away from the other whenactuated, driving means including .a rotatableelectric motor foractuating said: gripping and guiding means, said motor having a pair offield coils and an armature wit-h a lead from each connected together ata common point, said field coils being arranged in said motor in opposedrelation to each other so as to tend torotate said mot-or in oppositedirections when energized, means for connecting the opposite leads ofsaid field coils to said main conductors, respectively, for operation ondirect current, said last mentioned means including a resistor ofpredetermined value in eries relation with each field coil therebyproviding a secondary circuit between said'oond'uctors which includessaid common point, readily operable switch means connected across eachresistor and operable to eliminate the effect of said resistors insaid'secondary circuit when it is desired to operate said apparatus onalternating current, said secondary circuit also including a readilyadjustable resistor for controlling the normal spacing of saidelectrodes during the operation thereof, and means for connecting theother lead of said armature to said primary circuit at a point adjacenttheconnection of said one electrode to said ballast resistor.

RICHARD (3. BEITZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS -lumber Name Date 315,564 Sparrow Apr. 14, 18851,795,707 Blymyer Mar. 10, 1931 1,897,990 Smyser Feb. 14, 1933 2,057,521Harding Oct. 13, 1936 2,462,207 Mershon Feb. 22, 1949

